Subject: I-D ACTION:draft-shah-armd-arp-reduction-02.txt

From: [email-masked]
Date: Mon, 31 Oct 2011 09:00:05 -0700

A new Internet-Draft is available from the on-line Internet-Drafts directories.

    Title         : ARP Broadcast Reduction for Large Data Centers
    Author(s)     : H. Shah
    Filename      : draft-shah-armd-arp-reduction-02.txt
    Pages         : 11
    Date          : 2011-10-31
    
   With advent of server virtualization technologies, a host is able to 
   support multiple Virtual Machines (VMs) in a single physical 
   machine. Data Centers can leverage these capabilities to instantiate 
   on the order of 10s to 100s of VMs in a single server with current 
   technology.  It is conceivable that this number can be much higher 
   in the future. Each VM operates as an independent IP host with a set 
   of Virtual Network Interface Cards (vNICs), each having its own MAC 
   address and mapping to a physical Ethernet interface. These physical 
   servers are typically installed in a rack with their Ethernet 
   interfaces connected to a top-of-the-rack (ToR) switch. The ToR 
   switches are interconnected through End-of-the-Row (EoR) or 
   aggregation switches which are in turn connected to core switches.  
    
   As discussed in [ARP-Problem] the host VMs use ARP broadcasts to 
   find other host VMs and use periodic (broadcast) Gratuitous ARPs to 
   refresh their IP to MAC address binding in other VM hosts. Such 
   broadcasts in a large data center with potentially thousands of VM 
   hosts in a Layer 2 based topology can overwhelm the network. 
    
   This memo proposes mechanisms to reduce the number of broadcasts 
   that are sent throughout the network. This is done by having the 
   ToRs intelligently process ARP and frames, rather than simply 
   broadcasting them throughout the broadcast domain.  
    
   While this document addresses ARP, the Neighbor Discovery mechanisms 
   used by the IPv6 hosts that make use of multicast rather than 
   broadcast also pose similar issues in the Data Center. The solutions 
   defined herein should be equally applicable to hosts running IPv6.  
   The details will be specified in a subsequent revision. 

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